Mortgage Borrowing Power Calculator

Understanding Your Borrowing Power in 2026

Your borrowing power is the maximum amount a lender is willing to lend you based on your financial situation. It is determined by a complex calculation that weighs your income, living expenses, existing debts, credit history, and the lender's own risk appetite. Understanding how this calculation works is essential for setting realistic property budgets and making informed financial decisions.

In Australia, the Australian Prudential Regulation Authority (APRA) sets guidelines that all banks and authorised deposit-taking institutions must follow. One of the most significant rules is the serviceability buffer — currently 3% above the loan interest rate. This means if a lender offers you a rate of 6%, they must assess whether you can afford repayments calculated at 9%. This buffer exists to protect borrowers against future interest rate increases.

The serviceability ratio is another critical factor. Most lenders use a ratio of approximately 30% of gross income (some go up to 35%), meaning your total debt repayments — including the proposed new loan — cannot exceed this threshold. This is calculated at the buffered rate, not the actual rate, which is why many borrowers find their borrowing power lower than expected.

Why Borrowing Power Varies Between Lenders

Not all lenders calculate borrowing power the same way. While APRA sets minimum standards, individual lenders have discretion in how they assess income, expenses, and risk. Some lenders use the Household Expenditure Measure (HEM) — a benchmark for average living costs — while others rely more heavily on your declared expenses. Some lenders shade certain income types (like overtime or rental income) more conservatively than others.

This variation means that one lender might approve you for $650,000 while another approves $750,000, based on the exact same financial information. This is one of the key reasons why working with a mortgage broker can be advantageous — they understand each lender's policies and can match you with the one that gives you the best outcome for your specific situation.

For self-employed borrowers, the calculation becomes even more complex. Most lenders require two years of tax returns and assess income based on averages or the lower of the two years. Some specialist lenders, however, offer more flexible assessment for self-employed applicants, using only one year of financials or alternative documentation such as BAS statements.

The Impact of Interest Rates on Borrowing Power

Interest rates have a direct and significant impact on borrowing power. When rates rise, the buffered assessment rate increases proportionally, reducing the loan amount lenders will approve. Conversely, when rates fall, borrowing power increases. A 1% increase in rates can reduce borrowing power by approximately 10% — for a borrower on $100,000 income, this could mean $50,000-$70,000 less borrowing capacity.

In the current rate environment, borrowers should be mindful that rates may change over the life of a 30-year loan. Borrowing at your absolute maximum leaves no safety margin for rate increases or changes in your financial circumstances. Most financial planners recommend borrowing comfortably below your maximum capacity, ensuring repayments remain manageable even if rates increase by 1-2%.